Saturday, 28 June 2014

A Unique Form Of Fossil Parasite

The Mongolian grasslands.
On the Mongolian grasslands, cold temperatures during the winter, make for harsh conditions. The ground is often covered in a layer of frost, and herds of large mammals are hard pressed to find enough food to survive. Predators endure an even greater struggle.

Yet this all changes during the spring and summer months. The ice and frost melt and temperatures skyrocket. An expanse of grasses and sedges open up, giving herbivorous herds the sustenance they need to reproduce and raise healthy young. Predators, such as foxes and wolves, take advantage of these balmy conditions. All, however, must deal with a constant pest: biting flies.

The remarkable fossil of the 165 million year
old parasitic fly larva Qiyia jurassica
These parasites tap into blood vessels in the uppermost layers of the skin. All insectoid parasites use their mouths to clamp onto their food source. Yet millions of years ago, this was not always the case.

In Mongolia an insect with a unique method of parasitising its host was discovered at a locality near Ningcheng. The entire thorax formed a sucking plate used to latch onto its victim whilst using stinger-like mouth parts to extract sustenance. Its new scientific name, Qiyia jurassica, reflects this unique feeding method. The Chinese word Qiyia translates as 'bizarre'.

A reconstruction of Qiyia jurassica
The fossil itself was of a fly larva. At two centimetres long it was not much larger than the larvae of most fly species on Earth today, but its morphology was radically different. The head in comparison to the body was tiny and tubular, while the entirety of the thorax formed a sucker. The abdomen, meanwhile, supported a series of paired legs with small spines running along its back.

'No insect exists today with a comparable body shape,' said Dr Bo Wang from the University of Bonn. 165 million years ago Mongolia was covered by a series of shallow lakes interspersed with volcanoes. Within these lakes dwelt thousands upon thousands of salamanders whose remains can still be found, perfectly preserved, within the fine grained mud stones which formed on the lake beds. Fish fossils have not been found. Indeed fish are major predators of larvae and it is likely that their absence contributed to the success of Qiyia.

A plethora of different insect species, represented by over 300,000 fossils collected from the locality, shows the diversity of potential food sources available to support such a large salamander population. It seems that some insects turned the tables. 'The extreme adaptations in the design of Qiyia jurassica show the extent to which organisms can specialise in the course of evolution,' said Professor Rust, also from the University of Bonn.

Ecosystems are made up of animals and the plants they feed on. Anybody can call to mind an image of the African savannah populated by lions, elephants and gazelles or a coral reef housing all manner of fish and crustaceans. Yet it is not often appreciated that a single animal can constitute its own habitat and support an ecosystem. Parasites form intricate networks from within and on the surface - integral parts of an overarching biological community. If we are to reconstruct ancient ecosystems accurately, we need to take into account life at all scales, from animals to their parasites.